An unprecedented rise in the demand for food, rapid urbanization and climate change are significantly threatening global water supplies, according to a United Nations report, which stresses that a radical new approach to managing this essential resource is needed to be able to sustain future consumption levels.

The U.N. World Water Development Report, which will be launched at the World Water Forum in Marseille, France, estimates that there will be a 70 per cent increase in demand for food by the year 2050, leading to a 19 percent surge in water used for agriculture. Currently, 70 percent of freshwater is being used for agricultural purposes.

"Freshwater is not being used sustainably, according to needs and demands. In this context, the future is increasingly uncertain and risks are set to deepen." said Irina Bokova, Director-General of the U.N. Educational, Scientific & Cultural Organization (UNESCO), in the report's foreword.

The report, entitled "Managing Water under Uncertainty and Risk," notes that to respond to growing demand, countries have tapped into underground water sources, with water extraction tripling over the past 50 years. However, in some underground basins, water cannot be replenished and is now at critically low levels.

In addition, climate change will also have a growing impact on water resources as it alters rainfall patterns and soil humidity, melts glaciers and causes water-related disasters such as floods and droughts, which impact food production. The report estimates that by 2070, this impact will affect up to 44 million people all over the world.

The Chair of U.N.-Water, Michel Jarraud, stressed that "a collective response by the whole international community" will be needed to tackle the issue. The report emphasizes that without drastic action, water pressure will exacerbate economic disparities within and between countries, hitting the poor particularly hard.

"Unless water becomes a more central consideration in development planning, billions of people, mostly in developing countries, could face reduced livelihoods and life chances," UNESCO said in a news release. "Better governance of water resources is required, including investments in infrastructure from both private and public sectors."

The report also shows that despite projected increases in water demand, there are still nearly one billion people without such access, and this number is growing in cities.

"We have much to do before all people have the access to water and sanitation they need to lead lives of dignity and well-being," said U.N. Secretary-General Ban Ki-moon in a video message to the World Water Forum.

According to the report, sanitation infrastructure is not keeping pace with the world's urban population, and more than 80 per cent of the world's waste water is neither collected nor treated.